"use server";

import { revalidatePath } from "next/cache";
import { redirect } from "next/navigation";
import { getServerSession } from "next-auth";
import { authOptions } from "@/lib/auth-options";
import { prisma } from "@/lib/prisma";
import { slugify } from "@/lib/slug";
import { BillingInterval } from "@prisma/client";

async function assertAdmin() {
  const session = await getServerSession(authOptions);
  if (!session?.user?.id || session.user.role !== "ADMIN") {
    throw new Error("Keine Berechtigung.");
  }
  return session;
}

function parseBilling(v: FormDataEntryValue | null): BillingInterval {
  const s = String(v ?? "NONE");
  if (s === "MONTH" || s === "QUARTER" || s === "YEAR") return s;
  return BillingInterval.NONE;
}

export async function createCourseAction(formData: FormData) {
  const session = await assertAdmin();
  const title = String(formData.get("title") ?? "").trim();
  if (!title) redirect("/admin/courses/new?error=title");

  let slug = String(formData.get("slug") ?? "").trim();
  if (!slug) slug = slugify(title);

  const exists = await prisma.course.findUnique({ where: { slug } });
  if (exists) redirect(`/admin/courses/new?error=slug`);

  const description = String(formData.get("description") ?? "").trim();
  const authorName = String(formData.get("authorName") ?? "").trim() || session.user.name || "Admin";
  const published = String(formData.get("published") ?? "") === "on";
  const priceEuros = Number(String(formData.get("priceEuros") ?? "0").replace(",", "."));
  const priceCents = Number.isFinite(priceEuros) ? Math.max(0, Math.round(priceEuros * 100)) : 0;

  const course = await prisma.course.create({
    data: {
      slug,
      title,
      description,
      published,
      priceCents,
      billingInterval: parseBilling(formData.get("billingInterval")),
      authorId: session.user.id,
      authorName,
    },
  });

  revalidatePath("/kurse");
  revalidatePath("/admin/courses");
  redirect(`/admin/courses/${course.id}/edit`);
}

export async function updateCourseAction(courseId: string, formData: FormData) {
  const session = await assertAdmin();
  const title = String(formData.get("title") ?? "").trim();
  if (!title) redirect(`/admin/courses/${courseId}/edit?error=title`);

  let slug = String(formData.get("slug") ?? "").trim();
  if (!slug) slug = slugify(title);

  const clash = await prisma.course.findFirst({
    where: { slug, NOT: { id: courseId } },
  });
  if (clash) redirect(`/admin/courses/${courseId}/edit?error=slug`);

  const description = String(formData.get("description") ?? "").trim();
  const authorName = String(formData.get("authorName") ?? "").trim() || session.user.name || "Admin";
  const published = String(formData.get("published") ?? "") === "on";
  const priceEuros = Number(String(formData.get("priceEuros") ?? "0").replace(",", "."));
  const priceCents = Number.isFinite(priceEuros) ? Math.max(0, Math.round(priceEuros * 100)) : 0;

  await prisma.course.update({
    where: { id: courseId },
    data: {
      slug,
      title,
      description,
      published,
      priceCents,
      billingInterval: parseBilling(formData.get("billingInterval")),
      authorName,
    },
  });

  revalidatePath("/kurse");
  revalidatePath("/admin/courses");
  revalidatePath(`/kurse/${slug}`);
  redirect(`/admin/courses/${courseId}/edit?saved=1`);
}

export async function createModuleAction(courseId: string, formData: FormData) {
  await assertAdmin();
  const title = String(formData.get("title") ?? "").trim();
  if (!title) redirect(`/admin/courses/${courseId}/edit?error=module`);

  const max = await prisma.courseModule.aggregate({
    where: { courseId },
    _max: { sortOrder: true },
  });
  const sortOrder = (max._max.sortOrder ?? -1) + 1;

  await prisma.courseModule.create({
    data: { courseId, title, sortOrder },
  });

  revalidatePath(`/admin/courses/${courseId}/edit`);
  redirect(`/admin/courses/${courseId}/edit`);
}

export async function createLessonAction(courseId: string, formData: FormData) {
  await assertAdmin();
  const moduleId = String(formData.get("moduleId") ?? "").trim();
  const title = String(formData.get("lessonTitle") ?? "").trim();
  if (!moduleId || !title) redirect(`/admin/courses/${courseId}/edit?error=lesson`);

  const mod = await prisma.courseModule.findFirst({
    where: { id: moduleId, courseId },
  });
  if (!mod) redirect(`/admin/courses/${courseId}/edit?error=lesson`);

  let slug = String(formData.get("lessonSlug") ?? "").trim();
  if (!slug) slug = slugify(title);

  const contentHtml = String(formData.get("contentHtml") ?? "").trim();

  const max = await prisma.lesson.aggregate({
    where: { moduleId },
    _max: { sortOrder: true },
  });
  const sortOrder = (max._max.sortOrder ?? -1) + 1;

  const existing = await prisma.lesson.findUnique({
    where: { moduleId_slug: { moduleId, slug } },
  });
  if (existing) redirect(`/admin/courses/${courseId}/edit?error=lessonSlug`);

  await prisma.lesson.create({
    data: { moduleId, slug, title, contentHtml, sortOrder, published: true },
  });

  const course = await prisma.course.findUnique({ where: { id: courseId }, select: { slug: true } });
  if (course?.slug) revalidatePath(`/kurse/${course.slug}`);

  revalidatePath(`/admin/courses/${courseId}/edit`);
  redirect(`/admin/courses/${courseId}/edit`);
}